how to convert to apfs from Mojave

I have a mid-2012 13" MacBook Pro (best computer ever!! ;-) )running 10.14.6 and when I upgraded to Mojave it did not upgrade to APFS so I am not able to upgrade to Catalina (this computer will not upgrade to Big Sur unfortunately). I have looked at tutorials etc. but every time the APFS is still greyed out so I cannot convert the file system. Any tips on how to achieve this? I wouldn't worry so much except that this will be the last software update permitted unfortunately so I'd like the most recent version of GarageBand running if possible. I find it sad that a perfectly running (and fast) machine will become obsolete. Now I'm not a gamer or high volume video editing person so for me this computer is perfect. Unlike my PC of the same vintage that takes forever to boot up and crawl along. Anyway sorry for the rant :-P

I'd appreciate anyone pointing me to a link that I can follow to do the file conversion as so far I haven't found anything that's worked.

Thanks in advance for any support.

Susie

My computer specs:

Model Name: MacBook Pro

  Model Identifier: MacBookPro9,2

  Processor Name: Intel Core i5

  Processor Speed: 2.5 GHz

  Number of Processors: 1

  Total Number of Cores: 2

  L2 Cache (per Core): 256 KB

  L3 Cache: 3 MB

  Hyper-Threading Technology: Enabled

  Memory: 16 GB

  Boot ROM Version: 228.0.0.0.0

  SMC Version (system): 2.2f44

  Serial Number (system):

  Hardware UUID:

  Sudden Motion Sensor:

  State: Enabled

This is the hard drive I'm running:

Intel 7 Series Chipset:

  Vendor: Intel

  Product: 7 Series Chipset

  Link Speed: 6 Gigabit

  Negotiated Link Speed: 6 Gigabit

  Physical Interconnect: SATA

  Description: AHCI Version 1.30 Supported

Samsung SSD 860 EVO 1TB:

  Capacity: 1 TB (1,000,204,886,016 bytes)

  Model: Samsung SSD 860 EVO 1TB                 

  Revision: RVT03B6Q

  Serial Number:      

  Native Command Queuing: Yes

  Queue Depth: 32

  Removable Media: No

  Detachable Drive: No

  BSD Name: disk0

  Medium Type: Solid State

  TRIM Support: No

  Partition Map Type: GPT (GUID Partition Table)

  S.M.A.R.T. status: Verified

Volumes:

EFI:

  Capacity: 209.7 MB (209,715,200 bytes)

  File System: MS-DOS FAT32

  BSD Name: disk0s1

  Content: EFI

  Volume UUID:

AppleSSD1TB:

  Capacity: 999.86 GB (999,860,912,128 bytes)

  Available: 452.08 GB (452,078,362,624 bytes)

  Writable: Yes

  File System: Journaled HFS+

  BSD Name: disk0s2

  Mount Point: /

  Content: Apple_HFS

  Volume UUID: