You can say either "last year in May" or "in May (of) last year". The "of" is optional.
In future, please write the sentence in the main body of the post.
See above. Neither one is as natural as "I ordered this equipment in May 2022". I realise now that my suggestion of "last May" could be ambiguous - it could mean "May 2023" (literally the last May that happened) or "May 2022" (May of last year).