Thanks for you reply..
PSU of Dell Optiplex 9020 MT N-Series Desktop PC- Intel Core i7, to be replaced with Corsair RM Series RM650 650W ATX12V V2.31
Actually I am planning to buy CPU for video editing kind of stuff. and want to upgrade its GPU with GIGABYTE GV-N75TOC-2GI G-SYNC Support GeForce GTX 750 Ti 2GB 128-Bit GDDR5 PCI so since Dell 9020MT has power connector problem, could this solve the problem.