It looks like it has 32, 256k x 1-Bit DRAMs, which would make it a 1 MB SIMM. What’s unclear to me is how the 32 DRAMs are muxed into a 30-pin SIMM, which only has 8 data bits. Maybe those other two chips do some sort of chip select decoding based on address? Not sure. Either way, I think you’d need two of them, since the Plus has a 16-but data bus.