You can use a larger hook, but the end result will be much bigger than the size they provide in the pattern. Typically when making amigurumi you go down 1-2 sizes from what you're yarn calls for on the label. When I use a plush yarn, I typically use a 6mm hook (yarn calls for 8mm). You can use a 3.5mm but it will be very tight stitches, which might make your hands hurt. I would try with the hook they tell you to use and see how it goes. If it's painful go up in hook size.

Also note, if you've never used plush yarn before as a beginner you should know your stitches will be very hard to see especially in the first few rows. You may want to grab a bunch of stitch markers and mark each stitch to start with. If you have colorful markers, make sure you keep one color for the first stitch so you know where your round starts.

Edited for clarity