@AR_9812919
Refer -https://community.ptc.com/t5/PTC-Mathcad-Installation/How-to-convert-worksheets-created-in-earlier-v...
Fr more details you may also refer article -
https://community.ptc.com/t5/PTC-Mathcad-Installation/All-About-Mathcad-Software-Installation/m-p/70...
I hope the above details help.
Mathcad Prime 6.0:
https://www.mathcad.com/en/try-and-buy/mathcad-express-free-download/install
https://free-dl.ptc.com/install/pim_installmgr_mathcad.exe
Mathcad 15 M050:
https://www.ptc.com/-/media/Files/Docs/Mathcad/Mathcad15-EN.zip