how large is the biological structure of a virus?

These questions are easily “googleable.” Anyways, keep in mind that nanometer = one-billionth of a meter, and a micrometre (micron) is one-millionth of a metre.

>Viruses vary in diameter from 20 nanometres to 250–400 nm. Only the largest and most complex viruses can be seen under the light microscope at the highest resolution.

>Bacteria range in size from 0.2-2 microns in width or diameter, and up to 1-10 microns in length for the nonspherical species. The largest known bacterium is Thiomargarita namibiensis, with spheroidal diameters from 100-750 microns. Spherical bacteria as small as 50-500 nm in diameter have been reported.

>The cell membrane (also called the plasma membrane) is only about 7 to 9 nanometers thick and cannot be seen by the light microscope

>DNA molecules have a consistant width of about 2.5 nanometers (human hair has a thickness of roughly 20,000 nm to 180,000 nm), but the length of DNA molecules varies greatly.

Scientists usually describe the length of DNA using a unit called kb or kbp. One kb is 1000 base pairs, the base pair being the basic repeating nucleotide unit of the DNA chain. Each base pair has a length of 0.33 nm.

Bacterial chromosomal DNA length would be perhaps 3800 kb, or 1300 nm (1.3 microns).

The length of human chromosome number 1 DNA is 200,000 kb, or 67,000 nm (67 microns).

Of course, within the cell, DNA is coiled and condensed.

Hope this helped.