It is not easy to do because SUBSTITUTE doesn't allow to substitute a bunch of possibilities at once.

You will need VBA or if you can download a free addin from here: Morefunc then apply formula

=(LEN(A2)-LEN(SUBSTITUTE(A2," ",""))-(LEN(TRIM(REGEX.SUBSTITUTE(A2,"[a-z,A-Z]","")))-LEN(SUBSTITUTE(TRIM(REGEX.SUBSTITUTE(A2,"[a-z,A-Z]",""))," ",""))))