Sorry, I phrased my question really badly, I have no idea how to word it.

I'm looking to raise money for a charity at my local gym by completing 120km in one month. But I'm not sure if this is a good enough distance or too much? I'm just really rubbish with distances :( I usually go to the gym around twice a week, I'm 21 years old, female and relatively fit and healthy. Is this a realistic goal?

I realise I must sound stupid, I'm just looking for some advice with this, if anyone is able to help!