If you have a 290W psu you can upgrade to GTX 1650, GTX 1050Ti or 1050 without need to upgrade psu.

if you get the GTX 1650, make sure it is GDDR6 as there is another ver. having GDDR5.

you can upgrade memory to 16, 24, or 32 GB (you have two DIMM slots).

Do you have a suggested Product? The GTX 1650 with gddr6 comes on many cards, and some of them are saying 300w PSU... I just don't wanna buy the wrong thing lol. 

300 and 290W are basically the same.  these recommendations are ballpark figures.  If one day in the future you want to upgrade gpu further you can get a 24 to 8 pin adapter (off the shelf) for psu.

Another question, does it matter the size of card? Should I get the 'Slim' versions? Also, my computer is PCIe right?

Gpu has to be relatively short.  Chassis depth is 11.57 inch deep.  Minus front bezel your max gpu length is around 10 inch.  No need to be slim or single slot width.  Double slot width is fine.  Yes PCI e.

Thank you again! I'm gonna start shopping for the best deal/reviews. Seriously thank you.

It probably will.  Nvidia gpu system power recommendation is sometimes a bit exaggerated to accommodate all possible builds.  If you look at MSI spec for 1650 they mentioned 300W recommendation.  https://www.msi.com/Graphics-card/GeForce-GTX-1650-GAMING-X-4G/Specification
Also for future proof of this model look for Dell proprietary 460W psu upgrade. They have been out of stock for weeks to months so if you see one grab it.  I had to find an overseas source link for one desperate user.

Ok, so I went ahead and purchased a GIGABYTE Geforce GTX 1650 Direct X 12 GV-N16556WF2OC-4GD 4GB 128-Bit GDDR6 PCI Express 3.0 x16 ATX Video Card, It arrives Friday. It should work hopefully lol. I was gonna go ahead and upgrade the RAM all the way, What is the correct RAM? Should I buy it from Dell or is there like "performance" RAM? I know I can go up to 32GB, Thank you again for the guidance.

You do not have to buy from Dell but you want to make sure vendor has confirmed ram spec running in the Inspiron 3670.  Crucial claims so. “These upgrades are guaranteed compatible when you order from Crucial.com”

https://www.crucial.com/compatible-upgrade-for/dell/inspiron-3670

you may want to call them to confirm that. Ask if crucial ram does not perform at spec frequency in your pc, do you get your $ back.

So the GIGABYTE GEFORCE GTX 1650 just arrived after being majorly delayed, and I am encountering a pretty significant problem... It required a 6 pin supplementary power supply. I opened my case (for the first time btw) and there is no power supply cable, not even a non-6 pin. I thought this video card would work? I am confused and feel a little misguided. PLEASE HELP!

Ummm.... I would like some guidance... Please I bought this computer brand new and I bought the video card suggested to me, I would like to use them...

I have the same problem!  I have an Inspiron 3670 and I just installed Geforce GTX 1650 super.  I didn't see any unused power cable to plug into the slot at the top of it.  Did you figure out how to make this work?  I could always buy an external power supply to slip into the computer just to power it.

I am just adding to this thread with more up to date information.

1) You can use any GPU upto about 75W as long as it does not require the extra PCIe power connector. The best card in this category at this time is the GTX-1650 (NOT the 1650 Super which needs more power). However, as others have pointed out some manufacturers do require 6 pin connectors on the GTX-1650 cards. These may be factory overclocked? I am not sure if they will work well without upgrading the power supply.

Speaking of upgrading the power supply I highly recommend doing so. I found one for about $54. Here are the part numbers.

Optional OEM 365w PSU =
7VK45 365w, Huntkey
T1M43 365w, Delta

2) IF you upgrade to the OEM 365W power supply, you can install the GTX-1660 Ti or GTX-1660 Super with just a 6pin to 8pin PCIe power adapter. (NOTE: I strongly believe you could also use the RTX-2060 without a problem but I have not tested it. According to testing done at Tom's Hardware, the RTX-2060 NEVER draws more than ~9 Amps on the PCIe power connector, and the 365W PSU provides upto 11 Amps!)

3) No matter what graphics card you install, you do NOT need to make any BIOS changes. Just disconnect power, install the card, and update the drivers. It really is that simple now! (Some threads have incorrect information that claim you need to make changes in your BIOS)

Here is a link to the 6pin to 8pin PCIe adapter I used: https://www.amazon.com/Cable-Matters-2-Pack-6-Pin-Adapter/dp/B01DV1Z32Y

Here is a link to the Tom's Hardware testing I referenced: https://www.tomshardware.com/reviews/nvidia-geforce-rtx-2060-ray-tracing-turing,5960-8.html#:~:text=The%20GeForce%20RTX%202060's%2010.4,last%20generation's%20Pascal%2Dbased%20cards

@redxps630​ Hey Im in the same situation for fortnite, ive been told that ill probably need to upgrade if I wanna preform better, is a nvidia 1660 tiable to fit in an inspirion 3670