Here I show to enable archival policies in Form library.
Steps for enabling archival policies in Form library Open the form library, Go to Settings-> Form Library Settings Click on Workflow settings->Add workflow Add a Workflow in the form library by selecting the "ArchivalWorkflow" from the workflow listbox. Give some name e.g. "Archival" and make it workflow start manually. After setting the workflow configuration, go to Form library settings again and click on Information management policies setting under Permissions and Management section. Click on Define policy Click on checkbox Enable expiration . Select the field (e.g. Created) and time period(e.g. 3 Months).Select the action "Start workflow" and set the "Archival workflow". Done with the settings, now archival policy is ready.
SharePoint Framework (SPFx) A Developers Guide