• Convert copies of DNA to moles: DNA copy number can be converted to moles using Avogadro’s number (approximately 6.022×1023copies/mole).
• Convert moles to grams: Once you have the amount in moles, you can convert it to grams using the molecular weight of the DNA sequence. The molecular weight depends on the length and composition of the DNA sequence.
• Convert grams to milligrams
• Convert milligrams to milligrams per kilogram: If you know the mass of your sample in kilograms (kg), you can then convert the amount of DNA in milligrams to milligrams per kilogram (mg/kg).

Hi!

Just to complement @haidar's answer. Take into account that the average molecular weight of a nucleotide pair is 660 g/mol (or 660 Da)

Now you have all the required information for the conversion

Hope it helps! :)

Best regards

Francesc Estrany

To add a tiny bit more detail:

If you know the exact sequence of nucleotides, you can get the exact molecular weight (if you need that much precision).