Strip all letters from input field, leaving digits behind to be passed to a variable

Hey guys, I am working on a furniture delivery app and my users will be entering items to be delivered into various input fields. I’m trying to create logic that calculates the size of the load based on their inputs. I’ve managed to get it to recognise various key words and adjust load size but now i need quantity to be recognised as well.

I know I could create another input field specifically for quantity but I’d like to try and make the user experience as close to effortless as possible.

I’m wondering is there any way to create logic that strips out all letters and only leaves numbers behind which can be passed to my quantity variable automatically?

Thank a mill
Will