Different style guides may lead you to either an en or em dash. Our UK team goes en dash all the way, while our US folks favor the em dash.
Whichever you choose, the rules are the same:
Use a dash to separate out a phrase within a sentence—perhaps to break up the text or add emphasis—instead of commas or brackets. You can also use a dash on its own to mark a break in a sentence—try it instead of a semicolon.
Always use an en or em dash, not a hyphen, in a range like 30–40 (only use dashes if you’re doing a range of figures—use ‘to’ for things like ‘Monday to Friday’). And for those ranges, don’t forget to take the spaces out from either side of the dash.
If you type in a hyphen to separate out a phrase within a sentence, Word will generally autocorrect it to a dash. But sometimes you might need to put one in manually.