By default, MuseScore shows measure numbers at the start of each system except the first one in a section. Numbering starts at the first complete measure in a section.
if you wish to change measure numbering:
To always show the number of a particular measure, regardless of style settings, open Measure properties and select "Always show" from the Measure number mode dropdown.
To hide all measure numbers, uncheck "Measure numbers" in Format→Style→Measure numbers.
To hide the number of a particular measure, regardless of style settings, open Measure properties and select "Always hide" from the Measure number mode dropdown.
In Measure properties, check "Exclude from measure count" (in the Other pane).
In Measure properties, edit "Add to measure number". Both positive and negative numbers are accepted.
By default, numbering of measures always restarts at the beginning of a new section. To prevent this, and make numbering continuous, select the break and in the Properties panel uncheck "Reset measure numbers for new section".
To adjust the position of all measure numbers, edit the X and Y offsets of "Position above" and "Position below" in Format→Style→Measure numbers.
Note that any changes made to a measure number in the Properties panel may be lost if the layout changes.
Various properties for all measure numbers in the score can be adjusted in Format→Style→Measure numbers. Most are dealt with in the sections above.
Other measure-related pages: