Update dell inspiron 3650 GPU minitower

Good resientemente bought a dell inspiron 3650, and now want to upgrade or install a graphics card but looked and seen that I have a disability that is the source of power which says it can not exceed 240w, so and sought cards that you can install this source is the original that brings the pc but almost all cards ask a source of minimum 300w and so and seen can not update the source because there are no sources like this pc higher power, now and seen a video of a youtuber you install this pc (without changing the source) a amd 460 rx card (video here )so my question is if I can do this myself and if I can install a gtx 750ti to see the rx 460 is supposed to 750 watts you occupies less than 460 rx

my pc has: