I have received the three certificates(.CER files) to access the production server. How I am going to add/convert these certificates into PKCS12 file.
First export your certificates to a keystore and then import the keystore as a pkcs12 file. If you jave java installed you can use keytool command to accomplish both.
1) /jre/bin/keytool -importcert -alias cert1 -keystore keystore.jks -file Cert1.cer
2) /jre/bin/keytool -importkeystore -srckeystore keystore.jks -srcalias cert1 -destkeystore keystore.p12 -deststoretype PKCS12
Similar steps can be done using openssl too.