Ok, you need some SMART targets.
So
Specific - e.g. "find out what experience I need to get onto a SW course". Rather than "become a social worker"
Measurable - e.g. you will know when you have achieved it - e.g. ok so I need to find out about volunteering with Homestart.
Achievable - you could do it today by making a phone call to the college.
Realistic - Yep, phoning the college and asking them what experience they are looking for is realistic.
Time limited - You can say when you will have achieved it by - e.g. the end of today/lunchtime/by next Tuesday/within the next Month.
So contact the college again. Say that you are interested in applying for the SW course but that you understand that you need 120 hours experience. They won't remember speaking to you, but you will look like you've done some research (which you have) and they will know that you are serious. If they can't help you, ask to speak to the Course Leader or someone who can. They will know what they are looking for.
So ask them what sort of experience they are looking for.
Then when you have that information, you can start to plan your next SMART targets. And work towards those. It's really daunting to be faced with just
"I want to become a CP SW" because it is something that is going to involve lots of little steps to get you to where you want to be.
What they want is to know that you understand what is involved in SW - that you understand that sometimes it isn't pretty, that it's hard work, that not all parents are aware that they are having difficulties and that they are not all receptive to input. They want to know that you aren't going into it because you can't think of anything better to do.
21 is not too old to do anything.
I went to university at 26 and graduated at 29.
I retrained as a teacher in my early 30s.
It's never too late.