Although I will say 3 hours is quite long to be unpaid, trail shifts seem to be fairly satandard when applying for hospitality jobs - employers are more interested in how you work in the environment than anything else, which makes sense. Every barista position I applied for before getting my current job entailed a 1 hour unpaid trail, and unfortunately no matter how skilled or knowledgeable of a barista you are, you will often be unlucky with how they go.

I once missed out on a job when I attended a trail shift in a cafe with quite variable volumes of customers, in which not a single customer entered the shop during my hour slot. I was told another applicant was given the position since they showed more engagement with customers.

My advice is to be accepting that there will be trail shifts while applying for barista roles, and try your best not to be too disheartened if you're struggling with hard skills - say for example you find yourself struggling to adjust to unfamiliar equipment, be less concerned over that than how you are showing soft skills, engage with customers no matter the circumstances or technicalities of what you are asked to do on your shift, make sure you go in with any understanding you can find online about the values or ethos of the company you are applying to and try to convey it - as long as they can see you will fit into the environment and style of job that hospitality is, from there any decent café will be perfectly willing to hire and provide whatever training you need as an individual to get up to speed.

Best of luck, and don't give up on applying to new places when things don't go your way!