Can we use USB for Garphics card storage Improvment?

It is not likely that you can increase your Graphics memory. However, you could increase your system memory, which would result in better overall performance. For example, increasing your system memory would speed things up when you regenerate a drawing. But in order to achieve this speed improvement, you will need to use actual memory, not a USB drive which is acting like memory.

If you currently don't have enough memory, you will sometimes have bottlenecks ("traffic jams"), slowing everything down. In this case, anything which will alleviate the bottleneck will help. This is the one case where using a USB drive as memory will speed up your system. But since USB is a lot slower than actual memory, you would be a lot better off by adding actual memory to your system rather than by using a USB drive as memory.