You have to use the python distribution that comes with ArcMap (2.7.x) or ArcGIS Pro (3.5.x).
You can spend a whole load of time trying to patch a solution which is fine if you have more time than needs. The differences between 3.5.x and 3.6 or 3.7 won't manifest themselves as important for ArcMap or ArcGIS Pro.
Pro installs an Anaconda distribution which has been tailored to esri specifications.
I keep a separate Anaconda distribution (installed separately) for pure python work for 3.6/3.7 and associated models.
I would recommend you uninstall all versions of python, then install arcmap and ArcGIS pro... they will handle everything. You can then setup your favourite IDE to use either, but Spyder is sweet for working with Pro