Two plugins for Calibre to get .epub out of .ascm file:

DeACSM - https://www.mobileread.com/forums/attachment.php?attachmentid=195457&d=1659259613

Substitute of Adobe Digital Editions - turns .acsm into .epub. You need to register with Adobe ID.

DeDRM - https://github.com/noDRM/DeDRM_tools

Take down DRM of .epub.

With these two plugins installed you can just drag .acsm file to Calibre and get .epub without DRM.