Arm Compiler can not find "rl_usb.h"

I am trying to create a solution for an old project that uses AC5.

I followed the steps to set up the ARM environment within VSCode.

Then I converted the solution which didn't report any errors.

However, when I try to compile the code or build it, I am receiving 

/Users/atom/Work/lpclink/drivers/adchs.c:8:10: fatal error: 'rl_usb.h' file not found
8 | #include "rl_usb.h"
| ^~~~~~~~~~

/Users/atom/Work/lpclink/cm0_asm.s:6:2: error: invalid instruction
__TEXT__

/Users/atom/Work/lpclink/cm0_asm.s:7:2: error: invalid instruction
__THUMB_LABEL__
^
/Users/atom/Work/lpclink/cm0_asm.s:10:1: error: invalid instruction
FUNCTION_GLOBAL cm0_processAdc

Also, some assembly instructions seem to be unsupported by AC6. I tried looking at various migration guides but didn't find anything about USB as well as assembly instructions. Could you please direct me in right direction? If you need more information, I am happy to provide debug logs.