Well, it depends on your needs.
You may ask your distributor where you want to buy that hardware. They want to help you to get that deal.
One example:
If the hundreds of servers have only gigabit you might use up to 10x HPE 2930M stacked with stacking modules and stacking cables. Then add a 40 Gbit/s module in at least two of them for redundancy and connect your server with both modules via DAC cables.
The 2930M has up to 48 ports, so 480 servers + the one 40G server. Depending in your needs select different switches.
If you don't need the flexibility, but more throughput you should go with a modular switch.
You can find help on several vendors sites, but here I give you HPE’s solution for finding a switch if you want to do it all alone:
HPE Networking Switch Selector
Again: ask someone who sells that solution to you if he/she can help with the order. Otherwise, you might get in trouble when trying to put everything together and you notice that there are different power supplies, modules, cables that fit into different models. Some 2930Ms, for example, need more power than other 2930M models.