3.0l has a common issue with the Cam Synchronizer bushings wearing out and causing a squealing noise.
80k to 100k miles is average life of this part.
Google: ford ranger 3.0l Cam Synchronizer
If you want to test if that's the squealing then when engine is cold, remove fan belt from crank pulley, so it doesn't spin other pulleys.
Cold engine will be fine running for a few minutes without water pump.
Battery Light will come on, because alternator is not turning, that's OK as well battery won't go dead in a couple of minutes.
If you hear squealing replace Cam Synchronizer, it is in the old Distributor hole, Cam Position sensor sits on top of it.
If you know belt slipping is the cause of the squealing then you need to de-glaze ALL the pulleys.
Fan belt squeal means belt is slipping and that means a pulley is getting Glazed as belt slips on it, glazing is like ice for the belt, same as ice under your rubber tires, no amount of tightness or pressure will prevent new belt from slipping on "ice".
Use a wire brush or emory cloth to "rough up" all the pulleys, belt needs traction so it doesn't slip, same as your tires.