There's a bit of confusion here.
The R4M was the standard air to air rocket. R=Rakete, 4=4kg and M=Minenkopf.
There were various air to ground anti-tank weapons developed. The first was the 'Fliegender Panzerschrek' which as the name suggests was based on the infantry weapon of the same name. One was mounted under each of the ETC 71 wing racks carried by the Fw 190 F-8 and F-9. It had poor ballistic performance but it did become operational, first with 1./SG 10 in October 1944 and then III./SG 3, II./SG 2, 8./SG 1 and finally the rest of SG 10.
What people seem to be referring to above is a different weapon, the 'Panzerblitz'. Three versions were proposed but only the first saw service. The Pb 1 comprised the rocket body from an R4M mated with an 80mm mortar grenade (Gerate M8 ). Initially six, later eight, launch rails were fitted under the wings of the Fw 190s. By February 1945 there were 115 Fw 190 F-8s equipped to carry the Pb1 rockets. By this date 43,480 rockets had been produced and the production target was 16,000 per month. The first unit equipped with the weapon was III./SG 4 and its first operational use was on 7th December 1944.
By the middle of April 1945 3 and 6./SG 1, 9./SG 2, 6./SG 3, 7,8 and 9./SG 4, 1, 3 and 13./SG 9, 9./SG 77 and 13,/SG 151 were all operational with the system.
The Pb 2 was developed precisely because of the lack of armour penetration of the Pb 1. It was also based on an R4M rocket body but had a 130mm warhead supposedly capable of penetrating 180mm of armour. A few were tested on an Fw 190 F-9 but it was not used operationally. It was the proposed air to ground weapon for the Hs 132 and Junker EF 126, but we're in the realms of Luft '46 now.
The Pb3 again used an R4M rocket but had an 85mm hollow charge warhead. It certainly never became operational and I can't find any evidence that it was ever fired from an aeroplane, though I'll happily be corrected.
Cheers
Steve