I'll offer different answers.
FIRST, before you buy stuff, you need to check your motherboard's abilities. You want this new large HDD to be your "main drive", meaning you will boot from it. Well, to use all of any HDD over 2 TB you MUST have it Partitioned using the newer GPT system, rather than the MBR system. But to BOOT from such a unit your mobo MUST have a feature called UEFI Support, and that will need you to configure it a bit. A mobo lacking this feature cannot use a GPT-type HDD to boot from. So, verify whether you actually can boot from a large GPT-Partitioned drive. IF you don't have that UEFI Support in your mobo's BIOS, your alternative would be to keep your older HDD as your C: drive (assuming it is OK and your main aim is more space) and then buy and install a large second HDD. Since you are using Win 10, it will continue to boot from that old drive and it CAN Partition that new unit under GPT and allow you to use all its space. Win 10 just cannot solve the BOOT issue because the booting process requires that special feature in BIOS. Then you'd have two drives: one Partitioned in MBR format to use for booting without UEFI support in BIOS, and a second one over 2 TB Partitioned in GPT format to provide lots of space.
Now, IF you DO have UEFI Support in BIOS and thus CAN use a drive over 2 TB fully, the picture is much closer to what you want. I suspect strongly that some of the cloning utilities now offered for free by HDD manufacturers on their websites CAN handle the task of changing Partitioning systems. After all, the HDD makers want to make it easy for you to do exactly what you plan. To be sure, contact Tech Support at the company you choose and ask them specifically whether their utility can clone from an MBR drive to make a new GPT-style drive over 2 TB to boot from.
Here are a three points to know about this process.
1. Some HDD makers have free utility packages for download on their website to let you do the cloning operation for just this task. BUT each has customized the software so it only makes a clone TO one of their HDD units - they don't care who made your old drive. So if you buy a Seagate HDD, get their Disk Wizard package. If you buy a WD unit, get their Acronis True Image WD Edition package. In either case, check that you also get the instructional Manual document, and read it. These utilities can do a LOT more than cloning, and my next point is about using the menu systems to make a change, so you need to understand where the menus go.
2. As you start the cloning process, the first step is for you to specify the Source and Destination drive units. Make SURE you get this right because anything on the DESTINATION unit will be destroyed. You don't want to do that to the wrong drive! Then it will show you a proposed group of settings for the cloning operation, and ask you to approve and OK the job. Do NOT do that! In my experience, these tools often set up the sizes of proposed new Partitions on the large drive wrongly and fail to let you use all the new space, so you need to change those settings. If your old drive has two or more Partitions on it (one likely a System Reserved, and another large one that is your C: drive), the proposal will likely be to just duplicate the sizes, or maybe to make then new larger sizes in proportion to old sizes. That is not what you want, so there are maybe two changes to make:
(a) Assuming that the software allows it (you checked, right?), you will need to be sure it will do this using the GPT system, not the old MBR system.
(b) The size of the smaller System Reserved Partition does not really need to change - it will only contain the same stuff that was on the old drive's small Partition. BUT the new larger Partition to hold the C: drive should be made as large as possible to give you access to all of the new drive's space. Make those adjustments to the settings. When you're happy, THEN tell the software to go ahead.
Once the cloning has been done, shut down the system. Disconnect the old drive completely (leave it in or remove, as you wish) and connect the new larger drive to the SAME SATA port the old drive was on. Keep the old drive disconnected and unused for a while until you're sure that you got all your stuff copied off of it and don't need it any more - it is a perfect backup of your system up to the cloning time. AFTER that you can decide what to do with it. In the meantime, now that you have a new large HDD using the GPT system of Partitioning installed in your machine, you will probably need to boot directly into BIOS Setup and configure it to use the UEFI Support features on that new unit. You MAY also have to check that it is set up as your main boot device in the Boot Priority Sequence. When you've made your adjustments, don't forget to SAVE and EXIT from Setup so that the machine is permanently changed and can boot properly from the new system.