The length of the major arc LNM is 
<h3><u>Length of an arc</u></h3>
From the question,
We are to determine the value of the length of the major arc LNM
The length of the major arc LNM can be calculated using the formula

Where r is the radius
First, we will determine the value of the reflex ∠LKM
Reflex ∠LKM + ∠LKM = 360° (<em>Sum of angles at a point</em>)
From the given information,
∠LKM = 70°
Then,
Reflex ∠LKM + 70° = 360°
Reflex ∠LKM = 360° - 70°
Reflex ∠LKM = 290°
Also, from the question
r = 3 cm
Now, putting the parameters into the formula, we get

Then,


Hence, the length of the major arc LNM is 
Learn more on calculating length of an arc here: brainly.com/question/2005046