How do you get the new slots for new Bro-Mons?

Bro-Mon Bro-Mon Questions
1

I tried resetting, but it doesn’t work :smiling_face_with_tear:

2

rip

3

how do you unlock new backpack slots?

4

Idk

5

I lost 3 items cause of not enough backpack slots: booboo bandage, booboo bandage pro and pillow shield .but i have 5 pillow shield ultra