Hi Ashok,
For the purpose of PF coverage, if the management is the same or if there is a relationship between these 3 units, then you need to consider the total strength of the 3 units. Also, remember to include the headcount of all the direct and indirect employees associated with the company. As per your query, it is clear that the management is the same for all the 3 units. Hence, the count of all the 3 units should be considered.
Let me know if you need more clarification on this.
Regards,
Srini