Add milk, hot water and sauce mix (from Hamburger Helper™ box); stir to combine. Stir in uncooked pasta (from Hamburger Helper™ box) and tuna. Heat to boiling, stirring occasionally. Reduce heat; cover and simmer 5 minutes, stirring occasionally. Stir in frozen peas; cover and simmer 5 to 6 minutes, stirring occasionally, until pasta is tender and sauce is thick. Remove from heat.