Electrically if you use a 24-8 pin adapter for Optiplex 9020 that is c/w 3650.

physically ATX psu doesn’t fit 3650 case. It has to sit outside case, which is not practical 

@redxps630​ I am not worried about it sitting on the outside I could fab something to make work but do you think it will work ?also upgrading to gtx 1650 it needs a pcle 6 pin plug have installed in the tower and it fits perfect.I got the computer from my son for free so just trying to do some upgrades with out breaking the bank 

Pretty sure Optiplex 9020, 7040, Inspiron 3650 use same psu 8 pinout. It would work if the adapter is for Optiplex.

User validated mod of sfx psu inside 3650

https://www.dell.com/community/en/conversations/inspiron-desktops/inspiron-3650-upgrade-power-supply-unit/647f7dc8f4ccf8a8dec34e3a