I think your comments make it clear that the person has something called a "first-level volunteer license", and the person has also spent 100 hours as a volunteer, i.e. he has volunteered 100 hours of his time.
I haven't myself heard of a "first-level volunteer license", and I'm not sure whether it is defined by the 100 hours of volunteer time, or if those are two independent qualifications (the license and the time).
But since you don't offer other alternatives to the expression "first-level volunteer license", I'll assume that is the correct official name of the license.
If a person spends 100 hours volunteering his time, we would say he has performed (or "done", or maybe "worked") "100 volunteer-hours".
So you could say:
"Holds a first-level volunteer license with 100 volunteer-hours"
"Has a first-level volunteer license with 100 volunteer-hours"
"Has/holds a first-level volunteer license and has performed 100 hours
of volunteer service"
There are many other possibilities depending on the terminology used in this field. If people ever used the expression "100-hour volunteers" in English, they would probably be describing people who have volunteered 100 hours.
So you might even be able to say,
"Holds a first-level volunteer license as a 100-hour volunteer"
This would mean that he had that license, and he was a 100-hour volunteer, assuming "100-hour volunteer" is a commonly used term in the field in question.