Many of will always be followed by a word such as those, these, them, us, her, his, my, your, our, or the, and a noun, if needed. Many will only be followed by a noun or noun phrase without an article or pronoun.
The following examples show how many and many of are used:
Correct: Many kids from our school went to the park.
Correct: Many of the kids from our school went to the park.
Incorrect: Many of kids went to the park
Correct: She has many books about art in her studio.
Correct: She has many of her books about art in her studio.
Incorrect: She has many of books about art in her studio.
Correct: Many stores in town will be closed on the holiday.
Correct: Many of the stores in town will be closed on the holiday.
Incorrect: Many of stores in town will be closed on the holiday.
Correct: The storm made it difficult for many people to drive.
Correct: The storm made it difficult for many of the people/us/them to drive.
Incorrect: The storm made it difficult for many of people to drive.
Correct: Many toys were scattered around the room.
Correct: Many of his toys were scattered around the room.
Incorrect: Many of toys were scattered around the room.
Correct: The test was difficult for many students.
Correct: The test was difficult for many of the students/them.
Incorrect: The test was difficult for many of students.
I hope this helps.