+1 to Howard's way .... for a longer version ...
Site Admin Menu
Accounts
Browse a list of users
Add filters Course role is "Student" in any course from any category
Then go to Users Accounts Bulk User actions
Users in List - Select all in the filters
At the bottom of that form choose from the drop down menu, Download Click Go
Download Screen, Export users as csv
The csv file can be used to import into the other moodle.
Advise you look at it with a text editor
First line are the fields from mdl_user table.
Like: id,username,email,firstname,lastname,idnumber,institution,department,phone1,phone2,city,url,icq,skype,aim,yahoo,msn,country
'SoS', Ken