Converting Web of Science ID to pubmed or DOI
You can manually put parts of the citation into https://search.crossref.org/ and it will give you back the doi.

Alternatively, you could migrate your WOS bibliography into Mendeley using the steps in this video https://www.youtube.com/watch?v=FqtAPRZaz2U . I just started using Mendeley (by Elsevier) and have imported my EndNote references pretty easily. I was able to then find the missing PMIDs for a paper I was writing.

Good luck!