If you already have a version of Issue Picker Custom Field Type for Server/DataCenter, you can import all your issue pickers with their values, config and contexts to cloud using the Issue Picker Migration tool.
Go to Apps → Issue Picker Migration Tool
Select the json file by pressing the "Select file" button.
A report will be displayed with the information to be imported.
To proceed with the import, click on the "Import" button and the import process will start.