Proper cooling pad for ...

Usually Dell laptops don't exhaust to the bottom. Usually the bottom vents are air intakes and the fan(s) exhaust to the side or the rear. I looked in the service manual and it appears that your laptop exhausts to the rear, though it's hard to tell from the information there. You should be able to tell by holding your hand or face near the exhaust vent when the fan runs.

Heat and ventilation are issues with pretty well all modern thin laptops. You might want to do what I did:

I took a strip of lumber, about 3.5 cm. wide x 2 cm. high (1.5" x 3/4"}, and the length equal to the width of my laptop. I routed out two notches to accommodate the laptop's rear feet. The rear of the laptop sits in those notches, propping up the rear by 2 cm. That provides better ventilation underneath the laptop and makes it easier for the fan to draw in air via the bottom vent. 

It's cheap insurance, and also positions the keyboard at a slight angle that makes typing more comfortable. It won't solve a major heat issue, but it helps somewhat.

Dell Inspirons actually intake air from the bottom and exhaust through the vents on top or out the sides/back (or sometimes just out whatever holes it can find). I bought this last year, and it's fantastic. very powerful stream of air going right into that bottom intake vent:

https://smile.amazon.com/gp/product/B07NMBJVBG/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

It blows air right into that bottom vent, lowers my temps about 10C at least.

Unfortunately, attempting to sign in here again proves more problematic than the issue I first reported. Using my password and previous username, it refuses to allow me in so I have to create another username. This is nuts!

Anyway, I've attempted to find the exhaust ports and using a kleenex on the bottom of the machine, it proves that it is indeed venting from the bottom through a small rectangular vent. I've got to say, this is different. I would say, out goes the idea of using a cooling pad on this device. 

Hey, hope you are doing well for the dell using guideline, use these steps this will be helpful for you:

1. Turn off the computer.
2. Disconnect the power cable.
3. Check the air vents on the computer for dust or debris. The air vents may be located in different places. ...
4. Use a can of compressed air to blow the dust or debris away from the computer. CAUTION: It is recommended to use a can of compressed air only.

Or for more instruction use this link. This will guide you in a better way:

Dell Inspiron 15 3000 Series

Thanks for the reply. This Dell unit is brand new but just considered the cooling pad spite as it does get warm underneath. But it appears since the exhaust is at the bottom, using the cooling pad would be counterproductive.