how do I enlarge my on screen keyboard

To easily return the new Floating Keyboard to the normal on-screen keyboard presentation, use the two-finger “zoom” gesture (i.e., the reverse of the two-finger “pinch”).

If the Split Keyboard is restored instead of the full on-screen keyboard, you can either use two fingers (one on each of the two half-keyboards) and swipe the two halves together - or touch-and-hold the “keyboard” key, then slide your finger to the Merge & Dock option and release.

Use the floating keyboard on your iPad – Apple Support

Split and move the keyboard on your iPad – Apple Support

What does your onscreen keyboard look like right now?