Create a p12 file

openssl pkcs12 -export -out clientp12.p12 -inkey clientkey.pem -in clientcert.pem -certfile ca.pem

Create p12 file using openssl

 openssl pkcs12 -export -out client.p12 -inkey clientkey.key -in client.crt

-certfile ca.crt

or

 openssl pkcs12 -export -out client.p12 -inkey clientkey.pem -in client.pem

-certfile ca.pem

when it asks password give it and it will ask again to verify it and give it