Change a string in to a identical list

[Freeman Gilmore]

How to change a string in to a identical list.
>From  "-3 31 A -6 B -8"  to  (-3 31 A -6 B -8).    (Or from  ("-3"
"31" "A" "-6" "B" "-8")  to  (-3 31 A -6 B -8)  if it is simpler.)

Thank you, ƒg