How can you know the length of a hose that curves all round? Better get
one a few inches longer than what you think you need.I believe high
pressure hose is less than $3 /foot.

Find a clean place along the hose. The size of the hose is usually printed
on it. Sometimes the date of manufacture and  highest allowable pressure
is there,too.

You can put some  liquid soap on the crack and see if  bubbles are formed.
If it is a low pressure hose , and there are no bubbles, you may be ok.The
highest the low side will ever get is when the compressor is turned off(
and it is now, turned off).The system balances between high side and low
side then, and you may have only about 70 or 80 psi. The high side can get
up to about 250psi when running.  Test the high side if it is cracked ,
when the compressor is running.What caused the cracks?
Age, abrasion, dry rot?

Replacing a hose is not expensive, but the system needs to be discharged.

Good luck,Roger