Multiterm glossaries need to be exported out of Multiterm in a format that other tools such as Xbench or memoQ understand.
Launch Multiterm 2021. Go to File > Open Termbase and navigate to the folder with your glossary. When the file is open, go to the Termbase Management tab.
Select Export, then right-click on Default export definition and select Process
Follow the Wizard through to save an .xml export of the glossary.
For memoQ
You can import an XML file exported from MultiTerm directly into memoQ. See memoQ 9: Importing and exporting terminology for more details.
For Xbench
Load the exported XML to Xbench as Trados Multiterm XML glossary.