How do I change dot to arrow curser on iPad?

XWauwau is right. you cannot change the cursor to an arrow. But if you want to change the color or size of the dot as they suggested, instructions are here.

Make the pointer easier to see when using a mouse or trackpad with iPad - Apple Support

You actually cannot change the shape of your cursor on iPadOS. All customization possible is granted by the color and size of your dot. Sorry if you don’t like it

While the size of the dot-cursor can be altered, you cannot change its style from a dot (representing the “touch” point) to an arrowed pointer.

Available information about customising the Mouse/Trackpad pointer can be found here:

Use a Bluetooth mouse or trackpad with your iPad – Apple Support

Apple do invite submission of comments and feature requests via its Product Feedback portal. If you would like to see additional features and capabilities in a future version of iPadOS, this would be the appropriate channel through which to make such a request. For iPad and iPadOS:

Feedback - iPad - Apple