Thanks for the reply i have the MT version and my CPU is the Core i5 4590

What size is your 3020 - MT, DT, SFF?  I take it you might have an MT if you're looking at that little fat card.

I would Google the dimensions for that card and measure the inside of the 3020.  If you have an MT, there's a good chance it'll fit.  You have 12" in length to play with.  https://m.youtube.com/results?search_query=Optiplex+3020+mt+GTX+1650  Also, people have been regularly using the 1650 in MT Optiplex models.  So you'll see if full size fits or if LP version is needed.

One more step I'd like to take - What exact CPU do you have?  I want to male sure the 1650 is the best pairing for your CPU with the least amount of bottleneck, or suggest something else.  We don't want the CPU bottlenecking the GPU.

Please see screengrabs below.  10%+ is considered bottleneck.  9.12% isn't bad, but the GTX 1050 ti will give you a little less bottleneck.

3020 can accept up to 16GB DDR3-1600 RAM (8GB x 2), and the best processor it can take is an i7-4790. 

As for graphics card, a 4Gb card (such as the GTX-1050 or 1650) is your best bet. You could probably do a GTX-1660 (6GB) but that would really be pushing it. Anything higher than that and you'd max out your processor, causing throttling. Keep in mind, you may also need to upgrade the PSU, depending on what video card you choose. (You didn't mention what PSU you have)

I know sorry so specs currently are. Morovol atx case, OptiPlex 3020, i5-4570, ddr3 8gb, GTX 780 3gb, 500gb hdd. Psu is the i5-4570 right? Sorry super new to this. But what would you recommend changing about my specs to make it a good gaming experience for gtav fivem(modded version of gta) i lag a lot and have trouble loading in. I wanna be able to use my ddr4 16gb ram sticks I have they don’t currently fit and more storage.most likely gonna upgrade to the GTX-1650 looked it up and it’s in my price range for sure. Just don’t know what else I need to upgrade.

Asked you cuz you seem extremely knowledgeable compared to me not knowing my new ram can’t even fit my pc lol 

I have a OptiPlex 3020 motherboard in a morovol case and a GTX 780 3gb and wanna upgrade my graphics card to something that’s better for gaming. I literally only play Fivem( Modded version of grand theft auto5) and I lag sometimes can’t fully load things and wonder if I could upgrade the graphics card I also have 16gb ram that i tried to put in and it didn’t fit so I’d like to be able to find something compatible. Any help would be extremely appreciated. is my number if someone could help or respond on here whatever would be easier. Thanks

Pretty sure it’s just a hdd i don’t think it’s a ssd but I wanna get the Samsung 980 1tb ssd pcie 4.0 nvme m.2. Also I have a smart bx1 550w psu 

Indeed, use an SSD instead of an HDD.  Some things can be painfully slow with Win10 on HDD.  Exception is WD VelociRaptor 10,000 RPM and hybrid HDD's.  SSD is still a little faster than VelociRaptor and hybrids are expensive, making SSD the best bet.

Is your Win10 a fresh or somewhat recent install?  If it's been some years, a reload (fresh install) can also speed it up.  But I also still suggest/recommend SSD.

Optiplex 7010/9010 also have 4 DIMMS, but take 3rd gen CPU as compared to 4th gen for the 3020/7020/9020.

Thank you, CB. The drawback of all Dell 3### or 3## is like you said entry level chipset equipped with 2DIMM slots only. To upgrade to 16 gb, you have to acquire the more expensive 2x8 gb ddr3. Market price of 2x8 gb is higher than 4x2 gb.  If you had 9020/7020 which are high end/main stream tier, you would have 4 dimm slots easier and more economical to upgrade ram.