Microsoft Works uses the WPS format for text documents, which many word processors can't handle. (For example, if you email a WPS file to one of the many people who use OpenOffice Writer instead of Microsoft Word, they won't be able to open it). So you need to consider what word processing program you'll be using on your PC after you've mucked about with it.
If you'll be using Microsoft Word then you'll still be able to open them, as Word can handle files created in Works. However if you'll be using something else (or you think that you might need to forward some of your files to other people) it would make sense to change the file format first. (If you've got Microsoft Word available to you, you can open your files with that and then use the 'Save as' option to save them as either DOC or DOCX files. Otherwise convert them online, using Zamzar or a similar service:
https://www.zamzar.com )
If you've got other types of files generated by Microsoft Works (e.g. spreadsheets or databases), you might also need to convert them to other formats first.
Backing files up to OneDrive should work but I'd prefer to back them up locally, by using a USB memory stick.