Measures per page

Add page breaks every 4 measures.

But do you mean 4 measures per page or 4 measures per system? If you want 4 measures per system add system breaks every 4 measures.

Note that if you have a lot of music in your measures you may not be able to fit 4 on a system/page. In which case you may need to change the scaling in Format>Page settings.

See https://musescore.org/en/handbook/4/formatting and if you need more help, come back and attach the score.

Dear Uke,
I saw your question about getting 4 measures to a line.
The "Page Break" is the answer - but keep an eye on how
it looks. If there are many notes in the line, (eighth and
sixteenth notes) then 3 measures might be enough -
or if there are fewer notes (Whole notes or half notes)
then 5 or 6 measures might fit on nicely. Four measures
per line is often quite good - but it can vary. OK?
Jeff