Cannot install pkg_resources using pip

[Rich Shepard]

Python3-3.9.10 installed on this Slackware64-14.2 desktop. Trying to run
meson to build an application I'm told it's missing pkg_resources, which is
part of setuptools. The command fails:
# pip install setuptools
bash: /usr/bin/pip: /usr/bin/python3.7: bad interpreter: No such file or directory

There is no python3.7 here:
# ls /usr/bin/python3.7
ls: cannot access '/usr/bin/python3.7': No such file or directory

How do I clean this up?

TIA,

Rich