Planning to expand storage for my Acer Predator Helios ph315-55, what’s the easiest way to clone?

As both of your Predator PH315-55 M.2 SSD drives slots are of a PCIe 4x4 type read at 7500MB/s and write at 7000MB/s speeds, the best and quickest is to use the internal 2nd M.2 drive slot (forget about using an external M.2 to USB-C adaptor, as that is way too slow) and use the OEM Crucial recommended cloning software the Acronis True Image for Crucial software and clone the new Crucial 1TB - P3 PCIe 4x4 M.2 SSD drive that way, after the clone is done onto the Crucial 1TB P3 M.2 SSD drive, take the old M.2 SSD drive out and put the new cloned Crucial 1TB P3 M.2 SSD drive into the laptops boot M.2 slot, then put the unformatted 2nd Crucial 1TB P3 M.2 SSD drive into the 2nd M.2 slot.

Then boot the laptops OS with the new cloned OS onto the Crucial 1TB P3 drive. Afterwards and to be able to use the 2nd Crucial 1TB P3 M.2 SSD drive, you need to do this:

Step 1: Initialize the Drive 

1. Press Windows Key + X and Select Disk Management

2. Now, right-click on the drive that has been labeled Not initialized and select Initialize disk. 

3. Then select a partition style for the unallocated SSD and click on OK. It is recommended to choose the GPT partition. 

Step 2: Allocate the Drive 

Once the drive is initialized, the SSD becomes available for allocation and will be labeled unallocated. Here’re the steps to add a volume to your drive.

1. On Disk Management, right-click on the drive and select New Simple Volume.
2. On the Simple Volume Wizard, click on Next
3. The size for the new partition is set to its maximum by default. However, you can assign a desired size for it. 
4. Now, assign a drive letter for the volume. 
5. Choose the Format this volume with the following settings options and select your preferred File System, Allocation unit size, and Volume label. Then click on Next.
6. Click on Finish to start formatting the drive. 
7. Once done, the unallocated SSD will be accessible through the windows File Explorer.