For 4.5 you will use code promotion.   See this guide: https://www.netiq.com/documentation/access-manager-45/pdfdoc/admin/admin.pdf

31.6.4.1 Selecting Proxy Services and Protected Resources to Import When you select a proxy service for import, all protected resources associated with this proxy service are selected automatically. You cannot deselect any protected resources of a selected proxy service for import. Code Promotion validates the content you want to import in to the target system. If there is any issue, it displays validation errors. Code Promotion imports Access Gateway customization details if you have selected the option. If any issue happens during customization files import, the system displays a message. You can continue or cancel the import process at that point. To select proxy services and protected resources to import, complete the following steps: 1 The Code Promotion page displays the entire list of proxy services and protected resources from the source setup. Select proxy services and protected resources that you want to import. 2 Click Next. Continue with “Verifying the Component-Specific Configuration Changes” on page 1255.

My NAM Version is not the same, I have to copy the proxy service from NAM 4.5 to NAM 5.0.

Unfortunately it is a requirement for the export/import to work the versions must be the same.  You would need to upgrade your 4.5 environmnet to 5.0 for the import to be successful.  There is also a configuration import\export option when you click on one of the AG cluster members but this also requires that the target import be the same version.  If the source AG box is an appliance and the target AG box is a service install, that would also be problem....even when the versions are the same.