1 to 10 grams I would suggest. It rather depends on the pencil's measures.
You would weigh it using a mass balance.
A scale.
The units grams would be a good choice.
Ounces
Divide its mass by its volume.
You cannot. If you know the volume, temperature and pressure of a pencil, you will be no closer to knowing its mass!
A 3-gram pencil on the moon would have a mass of 3 grams and a weight of 4.9 millinewtons or 0.018 oz.
You would weigh it using a mass balance.
Grams
A scale.
Metric ruler
A pencil has more mass than a paper clip no matter how big the pencil is.
Not enough information. To calculate mass, you would need volume and density (mass = volume x density).
Because a pencil has a mass of a few grams.
The units grams would be a good choice.
Ounces
The shape of an object is not enough to calculate its density. You also need its mass and then Density = Mass/Volume.