I don't know in detail tbh, but I know he has said about a quota based system and greater co-operation with France etc.
https://www.theguardian.com/politics/2023/sep/14/what-are-labours-new-migration-plans
"What is Labour proposing?
While ruling out reversing Brexit, the party’s plans are focused on greater cooperation with the EU, a deal that has proved elusive for Rishi Sunak’s government.
Starmer indicated he could do a deal with Brussels involving the UK taking a quota of asylum seekers who arrive in the bloc in exchange for being able to return people who cross the Channel.
Labour also plans to pay for more asylum caseworkers to help clear the backlog of more than 175,000 asylum seekers awaiting an initial decision on their application."