My Wi-Fi shows a weak security.

iPadOS produces these information messages to indicate that the security settings are far from ideal.

This support page will describe the more secure (recommended) settings for WiFi:

Recommended settings for Wi-Fi routers and access points – Apple Support

It is possible that your WiFi Router is too old for you to be able to set more secure settings on the router - so you can either configure the most secure settings that your Router will support, or update your Router for something that provides better security features.

You contact your provider (if it is their modem/router) and ask them if they offer a more secure setting.