I've found an easier way, using the new TEXTSPLIT function in the most recent version of Numbers.

D3, filled down:
=PRODUCT(TEXTSPLIT(C3,"×")×1)
F3, filled down:
=PRODUCT(TEXTSPLIT(E3,"×")×1)
etc.
TEXTSPLIT splits the text at the delimiter ×.
The ×1 coerces from text to a number that can be multiplied.
You could also use VALUE, e.g.: =PRODUCT(VALUE(TEXTSPLIT(C3,"×")))
PRODUCT multiplies the numbers.
TEXTSPLIT - Apple Support
If you can't upgrade Numbers to the latest version (14.4) then you can use REGEX.EXTRACT as in previous post.
Use ; instead of , in the formulas if your region uses , as the decimal separator.
SG