=(left(A2,2)+mid(A2,4,2)/60+right(A2,2)/3600)*B2
This formula doesn't work systematically as the first part can be 1 or 2 digit numbers.
Ex : 7:30:00 and 11:00:00
For single digit hours, everything will be shifted and the formula will includes some ":" .
To be sure this formula works, you have to avoid format "duration" which can displays something like 7:30:00. "Automatic" format for the time will display 07:30 in my situation and the formula will work.