You need version 3.95 or above of Volunteers for Salesforce for V4S Mobile installation. If you don't find this version or above in the AppExchange, please use the link below to get the latest version of Volunteers for Salesforce..
Please login to your Salesforce instance with an ID that has Administrator privileges. Upgrade Volunteers for Salesforce to version 3.95 or above. Then install the latest version of V4S Mobile from the AppExchange..
The latest version of Volunteers for Salesforce is on Github. Click here and follow the instructions in the Install the V4S Standalone Package in the Setup and Configuration Guide.