Ten months after I had fallen ill my friend paid me a visit.

[tufguy]

Ten months after I had fallen ill my friend paid me a visit.

Could you please check my sentence?

 

[emsr2d2]

Ten months after I had fallen ill, my friend paid me a visit.

Could you please check my sentence?

See above. You need a comma. Also, without surrounding context I can't see why you used the past perfect. The natural standalone sentence would be "Ten months after I fell ill, my friend paid me a visit."

 

[tufguy]

See above. You need a comma. Also, without surrounding context I can't see why you used the past perfect. The natural standalone sentence would be "Ten months after I fell ill, my friend paid me a visit."

My friend paid me a visit, ten months after I fell ill. Is this sentence correct as well?

 

[emsr2d2]

It's OK though the comma isn't necessary. The sentence flows better without it as a simple statement of fact. The comma suggests a slight pause on the part of the speaker.