Hello Sandra

The mAh indicated shows how much "power" the battery can store. The phone will work regardless of this specification. The dimensions of the battery and a few other things are more important. As with most cordless phones, the dimensions are likely to be AAA.
A telephone is a somewhat special application for a rechargeable battery. It is usually placed in the charging cradle. Batteries don't really like this and lose their storage capacity more quickly. Phone batteries should be less sensitive to this. They are available from various brands and are usually clearly labelled with Phone, DECT, a phone symbol, etc.

You can't really go far wrong with such phone batteries. Your phone should actually work with them.

I hope I have been able to help and that you are happy with your new batteries and that they last a long time.