Oh sorry, I didn't realise you didn't already have a USB-MIDI interface. In which case, yes, you do need such a thing. However that then raises the question of whether you buy a cheap (and sometimes unreliable!) USB-MIDI that has only one port going out from the PC and then add a "thru" to then split that into multiple outgoing ports. Or do you go the whole hog and buy a multi-port USB MIDI interface in the first place?

For example I can HIGHLY recommend this because it is the one I have and it works brilliantly..

https://www.amazon.com/ESI-ESI-M4UEX-8-Port-MIDI-Interface/dp/B07HQLK5BP/ref=cm_cr_arp_d_product_top?ie=UTF8

The ESI M4UEX has eight 5 pin DIN ports on it. Unlike many (most?) MIDI interfaces where that would be fixed at 4 in and 4 out the ESI is "intelligent" in that it knows whether a port is an input or an output so it will split the 8 ports as any combination of INs and OUTs. So it can be 4 In 4 Out like a traditional interface if you want to use it that way but equally you might choose for it to be 1 In and 7 out or even go the whole hog and use it as 8 Out.

While that is not currently available via Amazon you can see that it still has 5 stars after 24 votes - there's a reason for that!

It will depend which country you are in but this UK supplier gives an idea of expected cost:

https://www.bax-shop.co.uk/midi-interface/esi-m4u-ex-8-port-midi-interface-with-usb-3-0-hub?utm_source=google&utm_medium=organic&utm_campaign=surfaces&gclid=CjwKCAjwq-WgBhBMEiwAzKSH6DgQGoZ43gW1ZNjZ9br4-7dOryJOER_kwcS-dr6uS_E3HEiEL8XDjBoCYBwQAvD_BwE

(just shy of US$140)