Stepping up three 3V3 outputs to 5V
Using diodes is a bit iffy because the MAX7219 requires max 0.8 V low and min 3.5 V high. Diodes will just manage this, but noise rejection will be compromised.
A simpler solution might be to use a 5 V logic gate IC with TTL input levels (0.8 V low, 2.4 V high) from eg. 74LS or 74HCT series.
If you only need to buffer 3 outputs then any IC with at least 3 non-inverting gates will be enough. Suitable candidates include (where 'x' = eg. LS or HCT):-

74x04 or 74x14 (6 inverters, wire pairs in series to produce 3 non-inverting buffers)

74x08 (4 AND gates, tie one input high to make non-inverting buffer)

74x34 (6 non-inverting buffers)

74x86 (4 XOR gates, tie one input low to make non-inverting buffer)

74x125 (Quad bus buffer, tie Enable input low to active output).