"I can see two disk in the New Datastore wizard."
This is the VMFS datastore creation process - this is not the correct place for configuring vSAN storage. vsanDatastore is created automatically when vSAN is enabled on a cluster and as these exist as 1:1 with each cluster there is actually no wizard for creating this.
"But, I only see a disk in the vSAN disk management."
Maybe one of the disks has partitions on it or is not marked as local device and thus won't be claimable until this aspect has been resolved (check if they're marked local and 0 partitions).