Application changing from single thread to Free rtos Multi threaded

I have a stm32 application which runs mainly by timer peripheral interrupt of around 5 milli second in the single threaded application environment. When I change the application into Free RTOS application ,does it need a timer to be implemented from Free RTOS side( I have created two tasks for the Free RTOS which mainly consist of two sequential functions(one for each task) from the single threaded application’s timer callback )? Because as per my understanding the scheduler will call the tasks in between the time slices allotted to each task.

The RTOS already has its own tick interrupt - but depending on the accuracy require you may be able to just use API calls such as vTaskDelayUntil() to get the timing you need.