The MB is not the problem. You did not state the form factor of the Optiplex and the largest PSU that any of the 3050 series has is 240W. The RTX 3050 recommended minimum PSU is 550W. Your PSU cannot handle the RTX 3050. If you have a 3050 tower you could possibly upgrade the PSU but would need a 24 pin to 8 pin adapter cable as seen here at the Amazon page. The other thing to note is that using the i3 with the RTX 3050 is not a great match and could cause bottlenecks in gaming for example.

JOCEAN has a good point.  Just to add that both 3050 tower and SFF use Dell proprietary 6 pin TFX psu for motherboard.  The tower chassis may accommodate a SFX psu upgrade while the SFF can only accommodate TFX psu upgrade.  If you use a non-Dell 24 pin psu, you need a 24 to 6 pin adapter.  But in the case of RTX 3050, the easiest and cheapest upgrade is Dell oem 360w psu which fits both tower and SFF like a glove.  And 360w is good for RTX 3050 based on basic psu calculator 

Load Wattage: 253 W
Recommended PSU Wattage: 303 W

the low profile 3050 will work fine,, have it in my 5050 with 240w supply,,  its pcie4 but work great in 3.0 slot , only 2 or 3 fps behind pcie 4 slot, also removed all hdd and use 1 ssd to use less power, 

MSI GeForce RTX 3050 LP 6G OC GDDR6X Low-Profile  draws only 70w,,