How to make a pattern larger:

The main pillow pattern is shaped in an oval 9"x11". There is a second piece in a smaller oval 4"x6" that is meant to be attached for an animals face. Can I just add stitches and rows in the middle of the pattern? If so, To what ratio? Thanks

Welcome to KH!
Which pattern are you following? Can you give us a link or a pattern name?
The number of stitches to add will depend on the stitch and row gauge you are getting with your knit swatch. An easy trick is to draw the shape you want in the finished size that you want and then knit to fill in that shape, increasing or decreasing where needed.

The pattern is “Cat Pyjama Case” from Zoe Mellor’s Knitted Toys book. I made it in the pillow version without the opening and it measured 11"x9" for the body. I’d like it to be about 20". Thanks

I would use the pattern and follow the increases until you have the size you want. You’re approximately doubling the length as I understand it. Once you’ve increased to the desired width, you may need to knit straight for the middle section and then start decreasing. if you take good notes about how frequently you increased you should be able to follow the same rate of decrease.
Since you have an idea of the dimensions you’d like to end with, it may also help guide you if you draw out the shape and match up the knitting to that shape as you go.
Very cute case!