Ipad air M3 compatibility with Straight Talk

You will need to contact Straight Talk directly and see if they can provide an eSim for the iPad. Even if they do use Verizon's infrastructure, it's still up to them to provide the data-only eSim for the iPad. And as shown in the link provided by Sherman previously, it is not one of the available carriers.

Do note, the cellular option on iPads is only for data (internet access). The iPad cannot send or receive SMS or RCS messages or place or receive cellular calls on its own. Those require an iPhone using the same Apple ID as the iPad.

Straight Talk is not listed here as a carrier that supports iPad data.

Wireless carrier support and features for iPad in the United States, Canada, and Puerto Rico - Apple Support

I don't show any mention of an iPad on their website. But, you'll want to check with your carrier to see if they support cellular data on iPad.