Which Macbook has the greatest number of ports for connectivity?

Connectivity to what? Network? Disk drives? Keyboards and pointing devices? External monitors? iPhones/iPads/iPod Touches?

Depending on the mix of devices you have a need to connect, will give us a better idea of what might be appropriate.

The current crop of USB-C based Macs can to provide many different kinds of port, but you have to get adapters from USB-C Thunderbolt 3 to other kinds of ports. But one USB-C Thunderbolt 3 port with the right ($250 - $350) adapter can drive two 4K monitors, Gigabit Ethernet, 4 USB3 ports, have a SD Card slot, have audio in and audio out, plus provide power to the Mac. And for the current generation Macs you get more than 1 of those USB-C Thunderbolt 3 ports

USB-C Thunderbolt 3 adapters run from a few ports for something in the plus or minus $50 range. As the price goes up, more ports are available and when you get to the $250 range, you can drive 2 external monitors with a single adapter.

You want to go to someplace like <https://everymac.com/> to see what current and previous generation Macs offered in the way of ports.

You an also go to <http://support.apple.com> and find out the configuration of current and older Macs.

Any Mac will do that job.

If it has USB-C ports, then get a USB-C to USB3 adapter, or just get a USB-C to Lightning cable.

If it has USB2 or USB3 ports, then there all you need is the USB to Lightning cable that came with your iPhones.

The ports are the least of your concern. You want to figure on how much storage you need. So part of your decision should be how much music/audiobooks (in storage terms), and how large is the storage in each iPhone, as you will need to have at least that much storage per iPhone, and you should figure on multiplying that by a 3 or 4 so you can have multiple backup copies.

You might also look at iMazing.com as they have an iPhone backup utility that works rather well via WiFi. There is a free version that just does backups, and a for pay version that allows you to manipulate the contents of your iPhone files (to what extent I do not know, as I only use the free version to do WiFi backups).

You would have to qualify that with what kind of connectivity. Most seem to have close to the same number of ports but if you need Firewire, or USB, or Thunderbolt, or...