Micah speaks to the people of Israel as if he were speaking to mountains that can hear him, so "hear" is plural. (See: [[rc://en/ta/man/jit/figs-apostrophe]])
Micah is speaking to these things as if they are humans. Micah is using the mountains, hills, and foundations of the earth as an eternal witness against his people's idolatry. (See: [[rc://en/ta/man/jit/figs-personification]])