Read beyond the distance
A distance alone does not tell you whether an event welcomes walkers. Look for an explicit walking category, the total time limit, intermediate cutoffs and when course support ends. Ask the organizer directly if the published information is unclear.
Think through the whole day
Allow for the journey to the start, time waiting and the way home afterward. Consider terrain and accessibility as well as distance. Choose an event that fits your current preparation and discuss individual training questions with a qualified professional.
Keep the arithmetic separate from the plan
Dividing the available time by the distance gives an average pace, but stops and delays also take time. An average is a planning reference, not a promise that a particular event is suitable. The pace calculator can help make that arithmetic clear.