You can't directly put units on any advanced control...
...But what you will see on PTC's own worksheets would be something like
x: [slider] and then x2 or xunits: x*cm.
And then you use xunits for any further calculation or input.
Edit: If the unit varies but you want to use the same slider every time, then... you can be a little more creative. I came up with something like this...

PTC Marketer for Creo and Mathcad. I run their YouTube channels, some Creo campaigns, and all Mathcad campaigns and communications.