Getting baybinbher own bed.

I’m a FTM. My baby girl is 5.5 months old. We’ve been bed sharing since she was 2 months old and now I wanna get her to sleep in her own bed. There’s a pack and play in our room and that where in trying to get her to sleep. No luck all week. (If you mind have any advice on that all is welcome I’m about to give up). Someone told me to get a mattress for it instead of having her sleep on that hard thing that it came with. It’s an Ingenuity smart and simple pack and play. Anyone know what mattress will fit it.