Looking on the internet deeply has found these results:

I attended many conferences is the most popular phrase on the web.

I attended to many conferences 10 results on the web	I attended many conferences 1146 results on the web More popular!
Some examples and use cases from the internet:	Some examples and use cases from the internet:
It doesn't look like this phrase is very popular! The search could not find any examples on the internet.	I was greatly encouraged to always step out of my comfort zone and push myself a step further. I attended many conferences worldwide and presented my work�... As a journalist, I attended many conferences about various subjects in countries such as Spain, The Netherlands, England, Germany, Belgium, Egypt, Lebanon,�... 2 days ago ... Rick became a professional member in 1975 and I attended many conferences with him. I feel pretty protective over the next generation of�... Jan 25, 2013 ... Although I attended many conferences as an invited speaker without being reimbursed for transportation and hotel expenses, almost always I�...

I attended to many conferences

10 results on the web

I attended many conferences

1146 results on the web

More popular!

It doesn't look like this phrase is very popular! The search could not find any examples on the internet.

I was greatly encouraged to always step out of my comfort zone and push myself a step further. I attended many conferences worldwide and presented my work�...
As a journalist, I attended many conferences about various subjects in countries such as Spain, The Netherlands, England, Germany, Belgium, Egypt, Lebanon,�...
2 days ago ... Rick became a professional member in 1975 and I attended many conferences with him. I feel pretty protective over the next generation of�...
Jan 25, 2013 ... Although I attended many conferences as an invited speaker without being reimbursed for transportation and hotel expenses, almost always I�...