This wont work.  7010 uses different power connections than 9020.  
Dear all,  Want to ask if it is OK to install the Dell Optiplex 9020 MT motherboard into Dell Optiplex 7010 MT case? Will all the front panel connectors compatible with the motherboard? Especially power switch and USB/audio connectors. Thanks, Michael 
install Dell Optiplex 9020 MT motherboard into 7010 MT case