Hi shahidbashir7861,
Async replication and Galera(PXC) replication are different replication method.
What you need to do is re provision the replica using PXB (Percona Xtrabackup, same product used for SST) with the procedure described here: How to setup a replica for replication in 6 simple steps with Percona XtraBackup - Percona XtraBackup
Do note that you won’t be converting the PXC node to async replication, but rather taking the PXC node out of the cluster and setting up an async replica from scratch.
If the replica does not need to be a PXC cluster then you should use Percona Server binaries rather than PXC binaries (same version) and comment all wsrep variables from the config file.
BTW we have a similar forum thread about this topic: Creating a Asynchronous replica from an existing PXC
Regards