Sizes of things

Cells

10¹⁴ (100 trillion) cells in the Human body
A typical cell size is 10μm, (0.01mm) some pollen is a bit smaller than that but is made of several cells. The cell membrane (wall) is about 10nm thick for animals cells.
The cell nucleus is 11-22μm and is typically about 10% of the total volume, so the cell would have to be about 50-100μm. Typical mammalian cell nucleaus has 3000-4000 pores of 100nm diameter.
Animal cells are on the borderline of visibility, they can be seen but only as a spec of dust.

E-coli single-cell organisms

Human cell with nucleus, about 30,000 atoms in diameter, the pores are about 200 atoms diameter, the ribosomes about twice that

The Angstrom is 0.1nm and is roughly the size of a typical atom (0.5A for Hydrogen to 3.8A for Uranium).
The distance between carbon atoms in β sheets in enzymes etc is roughly 5A (0.5nm).
This would make the cell nucleus in the region of 30,000 atoms diameter, and the animal cell 150,000 atoms.
The pores on the nucleus would have about 600 atoms around their opening.