The easiest way is to use sp_browsereplcmds in the distribution database  - pass in the publisher_database_id and also get the xact_seqno and command_id from the error in the Agent to pass in.
This stored procedure generally queries MSrepl_commands as the table has the article id and the xact_seqno.
You could try to figure it out on your own with MSrepl_commands. The error message would be in MSrepl_errors which also has the xact_seqno and command_id

Sue