Can I use different PSU on my Dell Optiplex7050? Because I want to put GPU that requires 300w of psu but my PSU is only 240w

This forum post has more information on a PSU upgrade.

You will have to verify if your unit uses 6 pin or 8 pin for the adapter.

https://www.moddiy.com/products/Dell-OptiPlex-3040-3050-3060-Main-Power-24-Pin-to-6-Pin-Adapter-Cable.html

https://www.moddiy.com/products/Dell-OptiPlex-7050-PSU-Main-Power-24%252dPin-to-8%252dPin-Adapter-Cable-%2830cm%29.html

Standard EPS12v unit with 24 AMPS on 3.3v rails and 150W combined 3.3v/5v rails works OUTSIDE the case.

You use an adapter and run the wires in the hole left behind by the removed power supply.

https://www.bestbuy.com/site/evga-700w-atx12v-eps12v-80-plus-bronze-power-supply-dc-dc-technology-black/6346160.p?skuId=6346160

No way Im paying $59 for 500W when 700W is $79

Just like this

https://www.youtube.com/watch?v=SCQTj1ei3Ew