Often times we get "vector" files with a "raster" graphic placed inside. Just because a file is .AI, . EPS, ect, does not mean it is a vector graphic. The easiest way to tell a vector from raster graphic is to simply zoom in.
Once you have your file open, hit Alt + 0 on PC or ⌘ + 0 on Mac to bring the artwork to front and center. Then hit Alt and + on PC or ⌘ and + on a mac to zoom in. Continue to hit +, and if the file stays nice and crisp around the edges it is most likely vector, if they start to pixelate then the file is raster.
You zoomed in and you have a raster file? No problem, often times we can still use them. To use a raster file preferably it is to the size it needs to be printed, and at 300dpi.
Once you have your file open in Photoshop, navigate in the Menu to Image < Image Size. That will bring up an Image Size menu, switch your dimensions to Inches.
What to look for is an image to the proper print size 8" x 8" in this case and at least 150 PPI
Dimensions That Work
Ideally you'll get a file that is to size and 300 PPI. But the real world is not ideal. There are many raster files we can work with, but knowing from the beginning will help speed production down the line rather than having to ask for new or better files.
If you open your image and it is on a huge canvas like 100" x 100" but only 100 PPI you can scale down the file to print size and change the PPI to 300 and the file would be usesable.
If an image is smaller than the size they want it printed but 600-1000 PPI you can typically scale it to print size and lower the PPI and the image will be useable. Say they send a file at 6"x6" and 600 PPI, you can scale this to 10"x10" and 150 PPI and the file is usable.
There are many instances when a raster file can be used, but we still prefer vector, and the more files you open the more you will start to see what will work and what won't.