Using substring and ltrim in Alteryx

I have the below sql code and want to convert this to alteryx formula and apply to dataset below. isnull(SUBSTRING(rtrim(ltrim(hhm.Surname)),2,1),'2 ') +isnull(SUBSTRING(rtrim(ltrim(hhm.Surname)),3,1),' 2') +isnull(SUBSTRING(rtrim(ltrim(hhm.Surname)),5,1 ...