Yes, you can. A 220V extension cord would come in handy when you need to move around while working on a project or your project has a large surface area, especially when your plug is short. It's not advisable to create a DIY extension cord, especially for something as heavy as a 220V MIG welder, and this leads to electrical hazards and accidents while welding.
Instead, do your research and look out for heavy-duty 220V extension cords that can take your welder without any challenges. You should also look out for added features like weather resistance and durability.