The tags appended to your post suggest that you have an iPad Air2.
Some older models of WiFi extender may be able to connect with your WiFi router, but will do so using older security standards that have been deprecated by Apple.
Unless your WiFi extender (and Router) explicitly support WPA2 (AES-PSK) as a minimum - with WPA3 being recommended - you are unlikely to be able to use the WiFi extender with your iPad. Mixed mode WPA2/WPA3, if supported by the Router, should be disabled.
Be aware that WiFi Extenders are not a good or bandwidth-effective method to extend a WiFi network; when using an Extender, you will halve the maximum effective throughput for every "hop" added to the network.
If you need to improve WiFi coverage, there are much better and more reliable methods to do so. The two most common - and recommended - are to:
a) add an additional Wireless Access Point (or Router configured in bridge mode), connected via an ethernet cable to your main Router.
b) replace your existing WiFi Router with a modern "mesh" router system - that uses one or more additional wireless/wired nodes. The additional units often use a dedicated wireless backhaul to the main WiFi Router - and your iPad can seamlessly and automatically switch to the mesh Router with the strongest or most reliable WiFi signal.