How to change layer paths in a mxd-project based on a sde file

There are ArcMap projects, and need to change the layer paths in these projects using the geodatabase connection file (sde file). How to do it? Note: the findAndReplaceWorkspacePath(old_sde_file, new_sde_file) function did not help.

Can use findAndReplaceWorkspacePath("", sdeFile):

import arcpy, os
def changeLayerFiles(fullPath):
    nameWithPath, extension = os.path.splitext(fullPath)
    if extension.lower() == ".lyr":
        layer = arcpy.mapping.Layer(fullPath)
        for lyr in arcpy.mapping.ListLayers(layer):
            lyr.findAndReplaceWorkspacePath("", sdeFile)
            #lyr.findAndReplaceWorkspacePaths(u"C:", u"D:") #do when need change name of disk
            outputFile = os.path.join(outputFolder, os.path.basename(nameWithPath) + ".lyr")
            lyr.saveACopy(outputFile, "10.3")
            arcpy.AddMessage("layer " + os.path.basename(nameWithPath) + ".lyr is change")
            del layer

if __name__ == '__main__':
    #input parameters:
    inputFolder = arcpy.GetParameterAsText(0) #folder with input files mxd 
    outputFolder = arcpy.GetParameterAsText(1) #folder with output files mxd
    #sdeFile = r"D:/gis2.sde" #do when need used locale sde-file
    sdeFile = r"\\10.64.68.36\j\ElectronicArchive\Connect\gis1.sde"
    for fileName in os.listdir(inputFolder):
        fullPath = os.path.join(inputFolder, fileName)
        if os.path.isfile(fullPath): 
            changeLayerFiles(fullPath)