=LEFT(B2,LEN(B2)-2)/10^((MATCH(RIGHT(B2,2),{"PB","TB","GB","MB","KB"},0)-3)*3)
to MB, handling error
=IFERROR(LEFT(D2,LEN(D2)-2)/10^((MATCH(RIGHT(D2,2),{"PB","TB","GB","MB","KB"},0)-4)*3),0)
