@PaulMcr — Welcome to the forum. Great question! Here are a couple of interactive tools that are helpful and instructive in terms of finding the right chords to fit your melody.
First, here is a site that shows the circle of fifths:
https://chordchord.com/circle-of-fifths
Also, here is a site that shows possible chord progressions, chords in a key, and the notes in chords:
https://autochords.com/
Both sites are useful when composing a song and searching for the desired chords. :D
Cheers,
Joseph