If you want to apply to a Masters Degree you need to show a Master Entrance Qualification, so usually an academic degree. In most cases this is a Bachelor's Degree and the respective transcript of records.
If your cumulative GPA is not listed on your transcript of records, then you also will need to include an official document from your previous university, which states your current/final cumulative GPA of your university degree.
Generally: Degrees from Universities outside Germany have to be at least equivalent to a 3-year (6 semester) Bachelor's Degree of a German University, in order to qualify as the Master Entrance Qualification.
The Entrance Qualifications for each Master Degree can be found in the „Fachprüfungsordnung“ of Trier University (German only).
Helpful information can be found here: Database on admission requirements (DAAD) or take a look at the Database anabin in order to see if a degree from outside Germany qualifies you to enrol to a Master degree in Germany (German only).
Within your application, you will also need to include your University Entrance Qualification (HZB) – in most cases the diploma of your secondary school.