Ole P Hovland

I have searched for the date/year of immigration for Ole P Hovland (b. 1817 to Per Hallvardson Hovland and Gunnhild Eiriksdtr Hola Hovland) and wife, Anna Oldsdtr Hatleberg (b. 1824/1825 in Laerdal to Ola Hatleberg and Brita Hallvarsdtr). Ole would have been from the Hovland farm at Ardal, Sogn, and I have in my information that Anna was from Laerdal area. I cannot find when they and their 3 children (Britha b. 1844, Guri b.1848 & Peter b.1952) came to America. I would appreciate any help available. Thank you.