IF and Arrayformula for google sheets

=IF(C2=""(vlookup('FBA Returns'!B:J,9,0),vlookup(C2:C'RMA Main Sheet'!D2:H,5,0)))

Need HELP!!!

IF "C" is blank, Vlookup "B" on Sheet 1, IF "C" is NOT Blank Vlookup Sheet 2.

also, turn this to Arrayformula and skip the return value row is NOT BLANK.

Please advise.