SSL pinning and client auth certification

Currently, I am using a capacitor in my project and I have added below plugin with Ionic native.

I have added .cer file in /certificates folder and also after ionic build this file is copied into /www/certificates folder but I am getting exception in android.

com.silkimen.http.HttpRequest$HttpRequestException: Trust anchor for certification path not found.

Actually, I need to add certificate which is .p12 password-protected file in my app. But I don’t know to use this with above plugin. So I am using .cer file for SSL pinning.

Can anybody help me with this?