I would like to run slow log 10 command in Redis cache to check which is taking so long time and I would like to know if it is possible to run the slow log 10 in azure portal or do we need to have third party app.

Azure Cache for Redis support most of Redis commands, including the SLOWLOG command.

And as @MarcGravell mentioned, Redis console in the Azure portal provides a secure way to run Redis commands. For more information about how to run Redis commands with Azure Cache for Redis, please check this doc: https://learn.microsoft.com/en-us/azure/azure-cache-for-redis/cache-development-faq#how-can-i-run-redis-commands-