Important: Volumes formatted as APFS can be read by a Mac running High Sierra, but not by a Mac running Sierra or earlier. Please see HT208018 - Prepare for. Then, to format a disk in Mac OS X or in MacBook Air running Mac OS sierra or High sierra you have to select your disk / pen drive you want to format in the left panel of the Disk Utility and select the ‘erase or delete ‘ tab.

There's 2 ways to do this, I prefer the first since it ensures you start with a macOS install. • Install the blank SSD in your Mac.

• Boot while holding ⌥⌘R for Internet Recovery. • Follow the steps to download and install macOS on your SSD. • During Setup Assistant, when prompted if you'd like to transfer your files, choose to transfer from a Time Machine backup.

• Follow the steps to important your content and settings from your Time Machine disk. Alternatively you can use the Time Machine backup for the initial macOS install. • Install the blank SSD in your Mac. • Connect your Time Machine backup disk. • Boot while holding ⌥ and choose your Time Machine disk from Startup Manager. • Follow the steps to install macOS on your SSD using the Time Machine disk.

You cannot just copy the Time Machine backup onto an SSD and expect to boot your Mac to the point of the last backup. You must first install MacOS on the SSD, then install the SSD into the MacBook Pro. Finally restore from the TimeMachine backup (you will be give this choice when you first boot from the OS on the new SSD). The trick is how to install MacOS on the SSD to begin with. My solution was to get an external USB to SATA adapter, then boot from the existing disk into recovery mode and perform a new OS installation on the external disk.

You may first need to format the external SSD using Disk Utility which you can do when you boot in Recovery mode. Once the the new OS is on the external SSD replace your internal disk with it, and boot up. During initial configuration it will ask you if you want to restore from a Time Machine backup.