I just switched to sbc hgih speed. I had at&t but I had an e-mail address at yahoo and I can't find it. how do

I had at&t world net. With this provider I went to yahoo and astablished an e-mail address. off this another address was added for my job to communicate with people at work for ignments and such. Now I can't find eather one. I also can't fine my messenger list of contacts.