How long to get quite fit?

Me and my friend did track events for 6 years and to make a long story short we quit. But after 3 years we want to start again, so we went out a 'run' yesterday and ended up walking/running for a combined time of 3 hours!
We want to get nice feminine toned tummys, we both are slim already and don't have a lot of fat, BMI is about 19/20 for me so I'm guessing she is the same, we go do this every second day? Is this good?)
How long to get quite fit?
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