Reindex part of a datastream

I January I added a field to a datastream. I sent the type to integer as it was a number (but not a count). I recently realised that searches on that field were slow as were visualisation. I then made the mistake of changing the type to keyword. Now I can't do any visualisations on the field at all, when I try I get a pop up saying that I have to reindex.

I had expected that I would no be able to visualise a time period which had both type but naively thought that it would work so long as all the data had the same type.

The question is how should I do the reindexing given that it is a datastream.

The data stream goes back several years and I have identified the first index where the field appears xxx-2023.12.24-000024 the last index which has the integer data is xxx--2024.04.13-000029. I.e there are 5 indexes which need to be reindexed.

It isn't clear to me now best to tackle this. I have learnt through painful experience that fiddling with datastreams can have bad consequence it you don't do it right! So I am seeking advice.