How to know how many Mount targets to create by Cloudformation

I create by cloudformation an EFS in a VPC, this VPC contains few EC2 instances.

I need to create as well mount targets for each subnet.

This cloudformation template can be executed in different AWS accounts. How to know how meny Mount targets resources to create?

I can have a vpc in account 1 with 3 subnets, another vpc in account 2 with 2 subnets...

How to make the template generic so that it's going according to every account environment ?

 "FileSystem" : {
       "Type" : "AWS::EFS::FileSystem",
       "Properties" : {
         "FileSystemTags" : [
           {
             "Key" : "Name",
             "Value" : "FileSystem"
           }
         ]
       }
     },

     "MountTarget1": {
       "Type": "AWS::EFS::MountTarget",
       "Properties": {
         "FileSystemId": { "Ref": "FileSystem" },
         "SubnetId": { "Ref": "Subnet1" },
         "SecurityGroups": [ { "Ref": "MountTargetSecurityGroup" } ]
       }
     },

     "MountTarget2": {
       "Type": "AWS::EFS::MountTarget",
       "Properties": {
         "FileSystemId": { "Ref": "FileSystem" },
         "SubnetId": { "Ref": "Subnet2" },
         "SecurityGroups": [ { "Ref": "MountTargetSecurityGroup" } ]
       }
     },