mehioo, In Project a resource IS a worker (or machine) but you're saying each resource has a number of workers. From that I conclude you really are talking about resource groups (e.g. laborers, truck drivers, etc.). If that is what you are talking about then here is an example.
Let's say you have 4 laborers of equal skill and the same standard rate. On the Resource Sheet enter a Max Unit value of 400% (i.e 100% for each of 4). Now you can assign up to 4 laborers to any given task without overallocating that group resource, assuming tasks to which they are assigned are not concurrent or overlapping. For example, if you need 3 laborers for the 1st task, assign the laborers group at 300%, you can then assign the remaining laborer in that group at 100% to another concurrent task.
If each of the individual workers in the laborers group resource has a different pay rate, then you will have to individually name each resource in order to give each a separate pay rate (i.e. you won't be able to use a group type resource).
If you are not talking about a group resource then please provide more detail so we can better understand what you mean. John