Formatting dates in power query

[Wezc85]

Hi all 

Im new to power query and am struggling to format a column with dates. Im taking the data from a work sheet which seems to have dates in both uk (dd-mm-yyyy) and US (mm-dd-yy) formats. In power query i have tried 'Using locale' date - united kindom. Some dates update ok, others get and error 'dataformat. Error:we couldnt parse the input provided as a date value'. And same thing if i try choosing US where some data works and same error above for remaining data. Ive searched numerous sites and YouTube videos and cant get it to work. Can anyone help? (i foubd a suggestion yo try splitting the data into seperate columns if i could differentiate UK and US dates but dont think i can) 

[HotChilli]

If you don't know which are UK and which are US, it's just guessing.  Can you find out from the source (business)?

You will need to solve that if you can, for example 4/3/2019 or 3/4/2019 are both valid dates in a single locale but they are a month out if you switch it the wrong way