Converting existing groups of 3 1/8 notes into triplets

I imported a score from via music XML (made by an ipad score scanning app) .

Although it worked reasonable, there a quite a number of triplets, which were not recognized and ended up as 4 groups of 3 1/8 notes in a bar.

The problem shows in the attached score from bar 23 onward (especially in the B part)

Is there a way in Musescore to convert the group of 3 1/8 notes in a proper triplet ???