In Calc, how do i retain only the numbers when a cell has numbers and letters

[gregors]

I have a column with numbers and letters (volumes with units).
I want to do calculations on the values.
How do I remove the space and the units so only numbers remain? Example of some of the contents in the column:

3000 ml

750 ml

330 ml

[gregors]

Just use the Edit>Find & Replace function.

Select the column

Call the function from the menu or < Ctrl+H >

Input " ml" (with space but without " ) in the “Search for” field and insure that the “Replace with” field is empty (not even a space)

Press the " < Replace All >" button

[JohnSUN]

Fastest way (using the mouse only)