Shut down your virtual machine ( Actions > Shut down).To perform that, perform the following steps: If you are unable to expand the virtual hard drive for some reason, an alternative solution would be to create a new virtual hard drive of the desired size and install macOS from your original virtual machine's recovery partition to that drive.

Then click Apply > Partition, and after a couple of minutes the operation will finish and the partition will be expanded.

Depending on the macOS version, you may need to do it using a graphical user interface (such as in macOS El Capitan), or by manually entering the value, to make it equal to the expanded disk size, and pressing Enter.

Increase the partition size up to the size of the disk.

Open Disk Utility, select the hard disk, click Partition. A notification regarding the necessity of making a backup of the virtual machine will appear.

Go to Hardware > Hard disk > Properties and move the slider to the desired value.Open the virtual machine's Configuration: click Parallels icon || > Control Center > right-click on the virtual machine > Configure.Note: make sure to create a backup of your virtual machine before performing these steps. How to increase disk size in a macOS virtual machine? Information

Mac hard drive space on mojave