Update iOS 13

Go to an Apple Store or your cellular provider store or Best Buy and buy a new iPhone.

Apple and most cellular providers do offer a trade in option. Check this link out --> https://www.apple.com/shop/trade-in?afid=p238%7CrTo88JDV-dc_mtid_1870765e38482_pcrid_78546500880246_pgrid_1256742275320989_&cid=aos-us-kwbi-brand--slid---product-

The iPhone 6 does not have the required hardware to update to iOS 13 or 14.

That would indicate that the apps you want or need have a requirement for iOS 13 or higher. If you need those apps, you will need a newer device.

To run iOS 14, you will need to purchase a model that is an iPhone 6S or newer.