The first Mars supply chain
When the round trip is measured in months, you do not ship what you need. You ship what you will need.
A supply line to the Moon can be reactive. If something breaks, the next vehicle carries the part. A supply line to Mars cannot work that way. By the time a request reaches Earth and a vehicle reaches Mars, more than a year has passed.
Pre-positioning
The Precursor mission delivered forty tonnes of power, structure and processing equipment to Mars orbit six years before any crew. The first people to arrive will find infrastructure that has been waiting for them, checked out and ready.
You cannot improvise on Mars. You can only have already decided.
Making it there
The supply chain that matters most is the one that never leaves Mars: propellant, water and oxygen produced from the atmosphere and the ground. Earth ships the plant once. After that, Mars supplies itself.