Cannot figure out how to connect unattached meshes in rig

Hi, I’m new to rigging in blender and when I created a rig for my character and tried posing it some parts of the character didn’t move with the other even though the bones are inside both of the seperated meshes. How would I make it treat them as one object? Here are some examples of what I am talking about:

you need to switch to Weight Paint mode and make sure that the bones have weight on these parts