What rail can I use with this handguard or will I have to buy a different one? Thanks

Buy a different handguard. One with a picatinnty rail.

I'm pretty sure you can get little sections of rail to attach to those, but because they're not rigidly mounted, you can use them for a sight of any sort, it's only be useful for something like a light or vertical foregrip.

you can fit a little section of PIC rail to the handguard but at 12 and 6 primarily

what is it your trying to mount , there may be other options. specifically if you want a light there are some very good front sight riser light mounts

you can do a MOE that will give you more places to easily mount accessories

you can also go with a quad rail , they tend to be a bit cheese grater on your hands

if you want a light this is a good option.

https://midwestindustriesinc.com/mi-tactical-light-mount/

and requires no modifications to your handguards

I was wanting to mount a bipod.

Harris does or at least used to make an adapter that allows you to mount a bipod on the traditional handguards. Be aware though that your point of impact when using the bipod will be drastically different than when shooting any other way in most cases. It would be better to install a free float forend if you wish to use a bipod.

yes this https://www.harrisbipods.com/product/no-5-adapter/

is the Harris bipod adapter

mounting the middle of the handguard made the least change for me shooting from the sling compared to the sling loop on the front sight riser.