internal loads: 8x250, 4x250 +aux fuel tank. AFAIR the 250kg bomb could be replaced by four 50kg bomb. Usually a set of four 250kg was replaced with a 50kg setup. This is H-3 to H-6, H-16 and later were often used with external load, don't know what they did with internal bomb bay (extra fuel?).
H-4 introduced external bomb racks, one or two capable of holding a 1t bomb each.
Somewhere around H-10 more external hardpoints were introduced, one central fuselage for the big ones (up to 2.5t) and four more around this for up to 500kg bombs (or 4x 50kg bombs each).
Maximum permisible load without reducing fuel was 2t for earlier, 2.5t for later He 111H (I assume the latter only with with 1400-1500PS Jumo 211 or 1750PS Jumo 213 engines)