I already removed and cut down this tree due to fire blight. My question is should I get rid of the dirt in the container that contains this tree. I've already washed the container to get rid of any potential problem.
I wonder if the fire blight problem is also infected the dirt. Thanks ahead for answering.

Yes, bag and dispose of the dirt in the trash. Look for fire blight resistant varieties of any replacement plant. It's probably best to just stay away from pears, apples, quince, etc.

Only this tree is affected, the rest I don't have a problem. I wonder if I can use this dirt elsewhere, not for growing apples or pears.

Fireblight is airborne not in the soil. You can use the soil for anything, you don't even have to sterilize the pot.

Are 100% sure it was Fire blight? I am asking because it's not a disease that will cherrypick its victims but will usually hit indiscriminately.

Fire Blight is a major problem for pears. Some varieties are highly susceptible. I have had more more trouble with Asian varieties than any other while old time varieties like Kieffer seem immune to it. It is a bacterial disease, so copper products will help. I don't know whether it will overwinter in the soil, but certainly all infected parts of the plant must be removed and disposed of. https://www2.ipm.ucanr.edu/agr...

Thanks all. Only this plant is affected, this one has lots of flower buds. The other didn't. I've Googled and the leaves are brown and dead, the trunk is also brown, fire blight problem. The Asian pear right next to it is not affected and so is the Anna apple, they didn't have any buds.
I don't have a lot of bin space to dispose the soil, this is why I ask this question. So to be safe, I will dump the soil.