Office 365 on Mac saving difficulties

My Mac Mini M1 OS 13.3.1.  This is my 4th Mac since 2007, have always used MS office programs, mainly word.  Lately, having much difficulty in opening, editing and saving.  Data retrieved from cd's; not able to select and transfer to a new .docx.

Info saved to CD's, no access to "Spotlight" search facility - why ?

A few days ago I paid for a new subscription for Microsoft 365 which appears to be different to the previous version of "Office" and I have not found any advice / description of any differences between them.  Do I just carry on with Word as per usual  ?