Hi and welcome to LQ
Most probably you didn't select make, (or anything from the development tools) when you installed Slackware. What you can do, is to mount the dvd and run (as root):
Code:
installpkg /mnt/dvd/slackware/d/make-3.81-i486-1.tgz
Slackware has a package manager, that is pkgtool and contains the various utilities (installpkg, removepkg, upgradepkg etc) used to deal with slack packages.