In cell B1: =MATCH(3,A1:A100,FALSE)
and in cell B2: =IF(ISERROR(MATCH(3,INDIRECT("A"&B1+1&":a100"),FALSE)),"",MATCH(3,INDIRECT("A"&B1+1&":a100"),FALSE)+B1)
copy B2 to B100.
This only works if your data actually starts at A1... if it starts on a lower row, you need a more general case.